Acousto-optic beam steering modulator for a projection system

ABSTRACT

An Acoustic-Optic A/O device receives light from a source and deflecting the light onto the second A/O device which may be a multi-stacked set of individual A/O devices. The first and second devices may deflected light according to control signals. Also, a multi-modulator projector display system including a light source, controller, an A/O modulator illuminated by the light source and capable of deflecting light according to controller signals, a second modulator illuminated by light from said A/O modulator and capable of modulating the A/O modulated light, said second modulator comprising a plurality of mirrors, and said second modulator capable of modulating the light according to controller signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 61/914,045 filed 10 Dec. 2013, which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to projector displays systems and, moreparticularly, to modulators for dual or multi-stage modulationprojection display systems.

BACKGROUND

In a conventional projector system, there is typically a single lightsource that illuminates a screen with an image that is modulated by someoptical system within the projector. When there is an image to beprojected that has a “highlight” (that is, a region of high brightnesse.g., a specular reflection off of a surface in the image, directsunlight, a luminant object, one region that is substantially moreluminant than other regions or the like), then the highlight would havethe same luminance level as the “full” screen. In that case, the lightcoming through the projector would have to be fully ON for the entirescreen and the projector system would have to “throw away” light that isnot a part of the highlight. This may not tend to be the most-efficientuse of the light source.

To address some of these inefficiencies, dual or multi-modulatorprojector systems are being proposed as a novel way of projecting imagesand video.

SUMMARY

Several embodiments of display systems and methods of their manufactureand use are herein disclosed.

An Acousto-Optic (A/O) modulator comprising a first A/O device and asecond A/O modulator is disclosed. The first A/O device receives lightfrom a source and deflecting the light onto the second A/O device. Thesecond A/O device may be a multi-stacked set of individual A/O devices.The first and the second A/O devices may the deflected light accordingto control signals from a controller.

In another aspect, a multi-modulator projector display system isdescribed comprising: a light source; a controller; an A/O modulator,said A/O modulator being illuminated by said light source and capable ofdeflecting light according to control signals from said controller; asecond modulator, said second modulator being illuminated by light fromsaid A/O modulator and capable of modulating light from said A/Omodulator, and said second modulator comprising a plurality of mirrors;and further wherein said second modulator capable of modulating thelight according to control signals from said controller.

Other features and advantages of the present system are presented belowin the Detailed Description when read in connection with the drawingspresented within this application.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced figures of thedrawings. It is intended that the embodiments and figures disclosedherein are to be considered illustrative rather than restrictive.

FIG. 1 is one embodiment of a dual modulation projector display systemthat may substitute its first modulator with an A/O modulator asdisclosed further herein.

FIG. 2 depicts a high level schematic description of a projector systemcomprising an A/O modulator as a first (or pre) modulator as made inaccordance with the principles of the present application.

FIGS. 3A and 3B depict a side view and a top view, respectively, of oneembodiment of an A/O modulator as made in accordance with the principlesof the present application.

FIG. 4 is one alternative embodiment of an A/O modulator with a lens inthe optical path.

FIGS. 5A and 5B depict a side view and a top view, respectively, of onealternative embodiment of an A/O modulator with multiple lenses in theoptical path.

DETAILED DESCRIPTION

Throughout the following description, specific details are set forth inorder to provide a more thorough understanding to persons skilled in theart. However, well known elements may not have been shown or describedin detail to avoid unnecessarily obscuring the disclosure. Accordingly,the description and drawings are to be regarded in an illustrative,rather than a restrictive, sense.

As utilized herein, terms “component,” “system,” “interface,”“controller” and the like are intended to refer to a computer-relatedentity, either hardware, software (e.g., in execution), and/or firmware.For example, any of these terms can be a process running on a processor,a processor, an object, an executable, a program, and/or a computer. Byway of illustration, both an application running on a server and theserver can be a component and/or controller. One or morecomponents/controllers can reside within a process and acomponent/controller can be localized on one computer and/or distributedbetween two or more computers.

The claimed subject matter is described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the subject innovation. It may be evident, however,that the claimed subject matter may be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form in order to facilitate describing the subjectinnovation.

Introduction

Dual modulation projector systems have been described in commonly-ownedpatents and patent applications, including:

(1) U.S. Pat. No. 8,125,702 to Ward et al., issued on Feb. 28, 2012 andentitled “SERIAL MODULATION DISPLAY HAVING BINARY LIGHT MODULATIONSTAGE”;(2) United States Patent Application 20130148037 to Whitehead et al.,published on Jun. 13, 2013 and entitled “PROJECTION DISPLAYS”

which are hereby incorporated by reference in their entirety.

In many dual, triple, more than 2-modulation (all of which arehereinafter referred to as “multi-modulation”) display systems disclosedherein use beam steering to put light on the modulation chips only whereneeded.

FIG. 1 is one embodiment of a dual modulating projector display system100, comprising two or more digital projectors (as modulators). FIG. 1shows a monochrome display 102 according to this example embodiment.Display 100 comprises a light source 102. Light 104 from light source102 illuminates a first light modulator 106. Light source 102 maycomprise, for example: a laser; a xenon lamp; an array of lasers (e.g.,diodes or otherwise) or other solid-state light emitters; an arc lamp;or the like.

In one embodiment, the first light modulator 106 may comprise aplurality of controllable elements 106 a e.g., on a fast switchingdevices, such as a MEMS device or the like. As will be described ingreater detail below (and in reference to FIGS. 2A-B and FIGS. 3A-C),elements 106 a may be selected such that they may be steered to reflectlight to a second modulator 110 by a suitable control circuit/controller116. The controller 116 may comprise a processor, a memory incommunication with the processor and such that the memory may compriseinstructions such that the controller may suitably control firstmodulator and second modulator (and other modulators, if they are in thesystem at issue) to perform the highlighting techniques as describedherein.

The set of controllable elements may also comprises a set ofcontrollable analog mirrors possibly with switching speeds sufficientlyresponsive to provide subframe rendering for processing highlights asdescribed herein. In one embodiment, the switching response time ofelements 106 a may be fast enough so as to reflect light onto the secondmodulator several times in a given frame of image data. For example,elements 106 a may affect a half frame, third frame, a quarter frame, or1/n frame illumination onto second modulator 110, as desired.

Light from first modulator 106 may pass through an optical system108—which may comprise sufficient optical components to perform adesired point spread function (PSF) of illumination onto secondmodulator 110. Depending on the ratio of elements 106 a in firstmodulator 106 to elements 110 a in second modulator 110, the desired PSFmay vary accordingly. For example, if the first modulator 106 is a MEMSarray and second modulator 110 is a DMD array, a typical MEMS array hasmany less elements 106 a (e.g., range from a few hundred to a fewthousand mirror elements, 100 to 2-3K) than a DMD array that may be afew million mirror elements thereon (e.g. over 500K mirrors and over).

Second light modulator 110 may be controlled by control circuit 116 (asfirst light modulator 106 may be) and comprise a plurality ofcontrollable elements 110 a. Each controllable element 110 a can becontrolled to select a proportion of the light that is incident on theelement 110 a from first spatial light modulator 106 that is transmittedto a viewing area 114 (through, possibly a second optical system 112).

In some embodiments, second spatial light modulator 110 comprisesoptical reflective or transmissive elements 110 a that can be switchedbetween ON and OFF states, e.g., a DMD device. In such embodiments,second spatial light modulator 110 may be controlled by a controllerthat sets its elements to be ON or OFF.

Transfer optics 108 carries light from first light modulator 106 tosecond light modulator 110. This light is capable of illuminating theentire active area of second light modulator 110 when all elements 106 aof first spatial light modulator 106 are ON. This light could spreadpast the edges of second spatial light modulator 110. Transfer optics108 may blur the light. Transfer optics 108 may be characterized by atransfer function which at least approximates how light issuing from apoint on first spatial light modulator 106 will be spread over secondspatial light modulator 110. The pattern of light incident on secondlight modulator 110 can be estimated or determined from theconfiguration of first modulator 106 (i.e. from which elements 106 a areON and which elements 106 a are OFF) and the transfer function. Asuitable projection lens 112 focuses light from second spatial lightmodulator 110 onto a screen 114 for viewing. Screen 114 may comprise afront-projection screen or a rear-projection screen.

Although the embodiment of FIG. 1 depicts a single light channel, itwill be appreciated that the first and second modulators may bereplicated for each of a series of color channels within the projectorsuch that each color channel includes 2 optically offset reflectivemodulators. The series of color channels may comprise a red channel, agreen channel, and a blue channel. The light source may comprise, forexample, a plurality of colored laser light sources. In one embodiment,the light sources may be modulated either globally (in brightness)and/or spatially (locally) dimmed according to signals (not shown) froma controller (e.g., 116).

The intermediate signals to the second modulator may be, for example,based on a light field simulation comprising a point spread function oflight reflected by the first modulator and the offset. For example, theintermediate signals to the second modulator may be based on a pointspread function of light reflected by the first modulator in eachchannel and the offset in each channel. The offset in the channels maybe the same, or the offset of at least two channels is different and theintermediate signals to second modulator in each channel is based on atleast one of the offset and differences in offset between channels.

Acousto-Optic Beam Steering Modulator Embodiments

As mentioned above, the first modulator may be a MEMS array and atypical MEMS array has a limited number of reflective elements (e.g., afew hundred to a few thousand). As a result, it may be desirable to findan alternative to a MEMS array as a first (or pre-) modulator for such adual (or multi-) modulator projector system.

In the projector systems of FIG. 1, the EDR projector may employ a“brute force” dual modulation approach to obtaining bright high contrastimages. Using this method, the full screen and highlight luminancelevels are equal, but it may be inefficient. Other embodiments ofprojector systems may employ triple modulation approaches that uses beamsteering to put light on the modulation chips only where needed.Conceptually this may work well, as only a small percentage of theenergy is required for the highlights; however, at present, there are nocommercially available beam steering devices with nearly enough mirrors.The optimal number is over 1500, and the largest devices have around200. The concept of beam steering is described in the attached document.In one embodiment, it may be possible to use triple modulation, with thebeam steering imaged onto a first DMD pre-modulator along with some base(flat) illumination.

Thus, several embodiments of the present application may address theseissues by replacing a first modulator comprising beam-steering mirrorwith an Acousto-Optic (A/O) modulator and/or deflector. In someembodiments, this A/O modulator may comprise two or more A/O devices. Inthat case, the A/O modulator may further comprise a single A/O device(which may be capable of handling a lot of power, but may have a lowTime Bandwidth Product (TBP)), and a second, multichannel A/O deflector.

FIG. 2 depicts a high level block diagram of a projector system 200 thatcomprises such a A/O modulator 204. Light from a source 202 may be inputinto A/O modulator 204 which may be controlled by controller 210 toilluminate the reflectors of the second modulator 206 (e.g. a DMD arrayor the like). Light from second modulator 206 may ultimately be used toform a projected image onto a screen 208. Controller 201, as shown, maybe constituted to provide control signals to the A/O modulator 204 andthe second modulator 206 or optionally to the light source 202 itself,depending upon input image data.

FIGS. 3A and 3B depict a side view and a top view, respectively, of asuitable A/O modulator 204. As may be seen, a first A/O deflector 302receives light from the optical path and may (e.g., under suitablecontrol signal from a controller) deflect the incoming light to a secondmultichannel A/O modulator 304. In one embodiment, A/O modulator 304 maycomprise a stack of a plurality of A/O devices 306. Light may bedeflected from A/O modulator 304 (e.g., under suitable control signalsfrom a controller) to a plurality of locations downstream e.g., to asecond modulator (which may be a DMD array).

Alternative Embodiments

FIG. 4 depicts a side view of one alternative embodiment of an A/Omodulator 400. As before, A/O device 302 receives light and may deflectthe light through to a lens 402 which, in turn, illuminates a second A/Odevice 304. If lens 402 is a Fourier Transform lens, then d₁ equals d₂.In that case, the transform of input light becomes well modeled in itsbehavior which may be desirable in many circumstances.

FIGS. 5A and 5B depict a side view and a top view of another embodimentof A/O modulator 500. A/O device 302 receives light and deflects it intolenses 502 and 504. In one embodiment, lens 502 may be a spherical lensand lens 504 may be a negative spherical lens (e.g., having no power).Light is thus focused onto one of many A/O devices in A/O stack 304.Light may thereafter be deflected into lenses 506 and 508. In oneembodiment, lens 506 may be a lens having no power and lens 508 may be aspherical lens. Light may then be focused onto another element e.g., DMDarray 510 for further modulation of light within the projector system.

Other Embodiments

As the various embodiments have demonstrated, it may be desirable toemploy the concept for using an A/O deflector and Multi-Channel

A/O deflector for beam steering. In many embodiments, the first A/Odeflector may allocate a proportional amount of light to each of thechannels in a second A/O multi-channel deflector, and provides for thevertical extent of the target (e.g., a DMD array). The multi-channeldeflector may provide the horizontal modulation, a single stripe foreach channel. In some embodiments, the system may employ a 6 channelmulti-channel deflector, but other sizes may be 8, 16, and 32 channelarrays.

In some embodiments, total optical path length may be about a meter,with the deflectors operating at about 2.5 degrees of deflection. Totalefficiency may be around 50-60%. In some embodiments, a collimated low

Etendue source such as a laser may be employed. Such a system mayallocate all of the light to a single location on the DMD within theconstraints of the resolution of multichannel deflector and number ofchannels. These deflectors may have TBPs in excess of 200. For oneexample, if a 32 channel array was used, this would provide for 200horizontal elements by 32 vertical elements, for a total of 6400 zonesof illumination. In some beam steering embodiments, substantially all ofthe energy may be concentrated into a single zone.

A detailed description of one or more embodiments of the invention, readalong with accompanying figures, that illustrate the principles of theinvention has now been given. It is to be appreciated that the inventionis described in connection with such embodiments, but the invention isnot limited to any embodiment. The scope of the invention is limitedonly by the claims and the invention encompasses numerous alternatives,modifications and equivalents. Numerous specific details have been setforth in this description in order to provide a thorough understandingof the invention. These details are provided for the purpose of exampleand the invention may be practiced according to the claims without someor all of these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

1. An acousto-optic (A/O) modulator comprising: a first A/O device, saidfirst A/O device receiving light from a source and deflecting the lightaccording to control signals received from a controller; a second A/Odevice, said second A/O device receiving the deflected light from saidfirst A/O device and further deflecting the deflected light according tocontrol signals from a controller; wherein said second A/O devicefurther comprising a set of A/O devices and said first A/O device iscapable of illuminating said set of A/O devices with said deflectedlight; and wherein further each of the A/O devices of the set of A/Odevices is capable of illuminating a number of addressable targets. 2.The A/O modulator of claim 1 wherein said second A/O device furthercomprises a set of stacked A/O devices such that said first A/O deviceis capable of deflecting light onto a first direction, said firstdirection moving along the axis of the stacked A/O devices.
 3. The A/Omodulator of claim 2 wherein said each of the set of stacked A/O devicesis capable of deflecting light onto a second direction, said seconddirection substantially perpendicular to said first direction.
 4. TheA/O modulator of claim 1 wherein said A/O modulator further comprises: aFourier transform lens, said Fourier transfer lens disposedsubstantially equidistance between said first A/O device and said secondA/O modulator.
 5. The A/O modulator of claim 1 wherein said A/Omodulator further comprises: a first optical set, said first optical setdisposed between said first A/O device and said second A/O device; and asecond optical set, said second optical set disposed after said secondA/O modulator.
 6. The A/O modulator of claim 5 wherein said firstoptical set further comprises a spherical lens and a negative sphericallens; and said second optical set further comprises a negative sphericallens and a spherical lens.
 7. The A/O modulator of claim 1 wherein saidaddressable targets comprise mirror of a DMD array.
 8. Amulti-modulation projector display system, said display systemcomprising: a light source; a controller; an A/O modulator, said A/Omodulator being illuminated by said light source and capable ofdeflecting light according to control signals from said controller; asecond modulator, said second modulator being illuminated by light fromsaid A/O modulator and capable of modulating light from said A/Omodulator, and said second modulator comprising a plurality of mirrors;and further wherein said second modulator capable of modulating thelight according to control signals from said controller.
 9. The displaysystem of claim 8 wherein said A/O modulator further comprises: a firstA/O device, said first A/O device receiving light from a source anddeflecting the light according to control signals received from acontroller; a second A/O device, said second A/O device receiving thedeflected light from said first A/O device and further deflecting thedeflected light according to control signals from a controller; whereinsaid second A/O device further comprising a set of A/O devices and saidfirst A/O device is capable of illuminating said set of A/O devices withsaid deflected light; and wherein further each of the A/O devices of theset of A/O devices is capable of illuminating a number of addressabletargets.
 10. The display system of claim 9 wherein said second A/Odevice further comprises a set of stacked A/O devices such that saidfirst A/O device is capable of deflecting light onto a first direction,said first direction moving along the axis of the stacked A/O devices.11. The display system of claim 10 wherein said each of the set ofstacked A/O devices is capable of deflecting light onto a seconddirection, said second direction substantially perpendicular to saidfirst direction.